CONTRACTION OF PUPiE. 283 



it acquires in thickness what it loses in extension : its 

 moisture, also, disappearing by evaporation, or more 

 probably by internal absorption, it becomes hard and 

 tough, like thin parchment, and of a dull reddish- 

 brown colour. The form is now that of an oblong 

 ball ; and it was from that circumstance termed an egg 

 by Redi and other early naturalists, — a term at which 

 Swammerdam takes great offence in this instance. 

 The various changes undergone by the included insect 

 were traced from hour to hour by Reaumur with his 

 usual patience and accuracy : but few of the minute 

 circumstances detailed by him would probably interest 

 our readers ; except that in casting its mandibles, 

 which are henceforth useless, they are not thrown off 

 on the outside of the case, but remain on the inside. 



Were such an extraordinary transformation as this 

 to happen to one of the larger animals, it would be 

 held forth as altogether miraculous. Were a lion or 

 an elephant, for example, to coil itself up into a ball, 

 compressing its skin into twice the thickness and half 

 the extent, while it remained uniform in shape and 

 without joinings or openings ; and, at the same time, 

 were it entirely to separate its whole body from this 

 skin, and lie within it, as a kernel does in a nut, or a 

 chick in an egg, throwing off its now useless tusks 

 into a corner, — and then, after a space, should it 

 acquire wings, break through the envelope, and take 

 its flight through the air, — there would be no bounds 

 to our admiration. Yet the very same circumstances 

 in miniature take place every day during summer, 

 almost under the eye of every individual, in the case 

 of the blow-fly, without attracting the attention of one 

 person in a million. 



The maggots of the genus of two-winged flies 

 {SyrphidcE) mentioned above as feeding voraciously 

 on aphides, do not, like those of the blow-fly, burrow 

 in the earth, but attach themselves to a leaf or a 



